The present invention is an improved form of Pank's U.S. Pat. Nos. 5,746,911, and 6,264,835, both entitled “Apparatus for Separating a Light From a Heavy Fluid.” Like these two devices, the present invention has three separate flow paths for influent water, and treats contaminated water at varying levels of efficiency, depending on the influent flow rate.
When it rains on a parking lot, a road, or other impervious surface, the water will not permeate into the ground as it once did, and instead this water will runoff and discharge directly into a stream or receiving body. Since these impervious surfaces typically have vehicles or traffic on them, an accumulation of pollutants will occur between rain events. This runoff is then concentrated because it is unable to be absorbed into the ground, and the pollutants are concentrated as well. This has caused a severe degradation of our watersheds. Most of the pollutants are typically washed off in the beginning (which is usually the less intense part of the storm), consequently the first runoff water is the most critical to treat. In an effort to minimize the impacts of this, systems have been developed to treat this water by removing the pollutants by separation or filtration.
Because precipitation occurs at variable rates from a small trickle to a monsoon, the system must be able to capture the pollutants and not release them during the high flow events. Consequently treating stormwater creates additional difficulties because the system must be able to clean the water yet be able to pass very intense storms or flooding could occur.